Inflatable air bags have consisted of several different designs, such as those made of material impermeable to the inflating gas. These rely on either blow-out patches to begin deflation of the bag or rely on holes of selected size to release the gas. In some versions, the holes may increase in size under gas pressure since the material of the bag is flexible. Other bags are made from a continuously porous material having one or more layers of varying gas permeability which stretch to some extent under gas pressure and thereby increase the gas release capability of the bag on full pressurization and occupant impact stress. Other generally non-porous bags have areas of porosity to release the inflating gas upon full deployment of the bag under gas pressure. Still other bags are elastic textile knit bags coated with a gas-impermeable coating to allow inflation of the bag, the coating of which cracks to become gas pervious when the bag stretches under gas pressure. The following U.S. Pat. Nos. discuss these various styles of bags of differing composition and are hereby incorporated by reference as to background and description: 3,799,574; 3,937,488; 3,807,754; 3,892,425; 3,618,981; 3,888,504; 4,097,065; 4,153,273; 4,169,613; and 4,360,223.
Gases are generated from an ignitable propellant, such as black powder, sodium azide or the like. Generally when ignition of such a propellant takes place gas is released into the bag, as well as burned, unburned and burning particles at the same time. Small size particles escape the air bag through the tiny or large holes built into the bag to allow release of gas for deflation of the bag into the interior of the vehicle, where they may harm the occupant. An azide type gas generator in an air bag floods the passenger compartment of a vehicle with a fine smoke of lung, eye, and generally mucous membrane-irritating particles of sodium oxide/sodium hydroxide and other fine particulate materials. Such gas generators are disclosed in U.S. Pat. Nos. 4,578,247 and 4,590,041, for example. Screen filtering and cooling devices have been utilized within the gas generating devices to try to remove the particles from the gas discharge. Problems of filter clogging and pressure build-up sometimes occur as discussed in U.S. Pat. No. 4,116,466. Problems of restriction of gas flow and reduction of deployment time of the air bag are disclosed in U.S. Pat. No. 4,131,299, where small vehicles require a faster deployment time of the air bag.
Once the gas generator is ignited, both gas and molten particles are released into the bag. The size and the amount of particles is dependent on the type of gas generator used. One standard receptacle for the gas is a Neoprene rubber-coated nylon bag which contains two deflation ports/holes on the side of the bag facing away from the occupant when the bag is inflated and deployed, such as described in U.S. Pat. No. 4,097,065. Such a bag acceptably inflates, then deflates under load (occupant impact on bag) but does not prevent the noxious combustion gases of bag inflation from entering the vehicle and subsequently the lungs of the occupant.
The present invention remedies the noxious particulate problem while maintaining the proper pressure curves of inflation and deflation under load removing or reducing the level of particulates entering the vehicle to a tolerable level.